HURRICANE ULIKA DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016
200 AM PDT WED SEP 28 2016
Ulika has continued to improve in organization, and recent microwave
data have shown that the cyclone has maintained a well-defined eye
in the 89-GHz channel during the past few hours. Hints of an eye
have also been observed in shortwave infrared imagery, embedded
within a compact central dense overcast. Subjective satellite
intensity estimates have risen to T4.0/65 kt from TAFB and T3.0/55
kt from SAB, and the objective ADT from UW-CIMSS is even higher
around 75 kt. A couple of CIMSS AMSU intensity estimates also
provided values of 60-65 kt several hours ago. Based on these
data, Ulika is upgraded to a hurricane with 65-kt winds, and this
could be conservative.
Ulika has rapidly intensified during the past 24 hours, which in
hindsight was probably helped by the cyclone's small wind field and
radius of maximum winds. Vertical shear is expected to remain low
for another 12 hours or so, which could allow Ulika to intensify
some more in the short term. By 24 hours, however, southwesterly
to westerly vertical shear is forecast to increase markedly,
exceeding 30 kt in a couple of days. Given Ulika's small size, the
cyclone will be particularly sensitive to the increase in shear,
and its intensity is likely to decrease quickly. Ulika is expected
to become a remnant low by day 4 and then dissipate southeast of
the Hawaiian Islands by day 5. The NHC intensity forecast is very
close to the intensity consensus for the entire forecast period, and
is higher than the previous forecast during the first 36 hours to
account for Ulika's recent intensification trend.
A mid- to upper-level low northwest of Ulika is steering the
hurricane north-northeastward, or 030/6 kt. Ulika is expected to
turn northward and northwestward around this feature during the next
couple of days. After it becomes a weaker system, it should then
come under greater influence from the low-level trades, turning
west-northwestward and westward on days 3 and 4. With the
exception of the GFDL, which is well north of the rest of the
guidance suite, all of the track models are tightly clustered
during the forecast period. The NHC track forecast is therefore
close to the various consensus aids and not too different from
the previous advisory.
Tropical Storm Ulika Advisory Number 004
Issued at 1100 PM HST MON SEP 26 2016
SUMMARY OF 1100 PM HST...0900 UTC...INFORMATION
-----------------------------------------------
Location: 12.1N 140.4W
ABOUT 1105 MI...1780 KM ESE OF HILO HAWAII
Maximum sustained winds: 40 MPH...65 KM/H
Present movement: N or 350 degrees AT 3 MPH...6 KM/H
Minimum central pressure: 1004 MB...29.65 INCHES
TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192016
800 AM PDT MON SEP 26 2016
Scatterometer data from around 0600 UTC indicated that the area of
low pressure located near 140W had a well-defined circulation, with
peak reliable wind vectors of 28 kt. Deep convection associated
with this system has since become much better organized. Satellite
classifications are T2.0 and T2.5, and the low is designated as a
tropical depression based on these satellite data.
Light northwesterly shear, warm waters of around 28 deg C and an
increasingly diffluent flow aloft over the cyclone support
intensification during the next 2 to 3 days. The large divergence
expected over the depression is related to a mid-level cyclone seen
in water vapor imagery near 18N 140W that is forecast to retrograde.
The only negative factor is marginal mid-level moisture that
is forecast to decrease further. Once the system gains sufficient
latitude after 72 hours, it is likely to become vulnerable to much
stronger westerly flow aloft. In fact, with 30 to 40 kt of westerly
shear forecast over the cyclone by day 4, rapid weakening should
occur, and the system is forecast to be a remnant low by that time.
The NHC intensity forecast is a blend of the statistical and
dynamical guidance through 72 hours and is below both sets of output
after that time.
The low was moving just south of due west during the last 24 hours,
but appears to have recently turned toward the northwest. Given
the sudden change in heading, the initial motion estimate of 305/04
is rather uncertain. Global models show the cyclone turning
northward within 24 hours and then moving north-northeastward after
that for the next few days while it rotates around the mid-level
low to the northwest of the cyclone. Once the cyclone weakens
appreciably after 72 hours, a turn toward the west is likely when
the remnant low is steered by the trade wind flow. The NHC track
forecast is a left of the multi-model consensus, close to a
consensus without the GFDL model.
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